New techniques developed during this year include ways to obtain both quantitative autoradiographic (QAR) and histological images from the same tissue section (co-imaging) and to perform simple chemical extractions of radioactive materials on QAR sections to determine the extent of tissue binding. Blood-tissue distribution of misonidazole, a radiosensitizer, apparently is limited mainly by blood flow within tumors. The inhalation of 20% CO2 appears to modestly open the blood-brain barrier (BBB) to water-soluble, relatively impermeable compounds. In studies with the ASV primary brain tumor model, blood flow (F) was sharply diminished only in the large tumors, whereas the blood-tissue transfer rate constant of AIB (Ki) was clearly increased in both large and small tumors. Glucose utilization (R) by the ASV tumor was relatively normal in the small tumors but elevated nearly two fold in one large tumor. The uptake and binding of tracer thymidine in brain and ASV-induced brain tumors was limited; significant bindings occurred in some, but not all, large tumors. All of our studies indicated marked differences between and within these tumors for F, K, and R as well as misonidazole and thymidine distribution.